1. Field of the Invention
The invention pertains generally to non-impact recording and more particularly to recording on electrophotographic recording media.
2. Brief Description of the Prior Art
In U.S. Pat. No. 4,885,597, there is described non-impact printing on electrostatographic recording medium. The non-impact printing described therein uses light-emitting diode (LED) printheads to record by modulating charge on an electrophotoconductive medium.
Light-emitting diode (LED) printheads typically consist of a linear array of LEDs arranged such that the pitch between LEDs is equal to the printhead resolution. The LEDs are arranged in the cross-track direction with respect to the path of movement of the photosensitive recording medium which enables an entire line of data to be exposed in parallel. If subsequent lines of printing-exposure data are activated at subpitch intervals, then the apparent resolution of the printhead is increased in the in-track direction (i.e., the direction orthogonal to the LED array and in-line with the path of movement). This technique is called multiple-address recording. Multiple-address printing increases the addressability of the printhead which provides a higher density of dots per inch. Currently, multiple-address recording is limited to the in-track direction only. The only way to increase the address,ability of the printhead in the cross-track direction is to increase the resolution by increasing the number of the LEDs per unit length. Increasing the number of LEDs will increase the burden of the driving electronics. In addition, increasing the number of LEDs exacerbates the problem of array and tile butting (alignment) errors. The LEDs are formed on chip arrays of say 128 LEDs in each array. The plural arrays are then assembled into a row of arrays to form a single row of several thousand LEDs. Where the LEDs are made closer together on each array, the butting of adjacent arrays becomes more difficult in attempting to maintain a uniformity of pitch distance between LEDs at the ends of adjacent arrays. Groups of LEDs may be assembled onto tile modules and the same difficulty obtains in spacing of LEDs at the ends of the modules when the modules are assembled onto printheads.
It is therefore an object of the invention to provide an improved method and apparatus for multiple address recording that increases cross-track image resolution without increasing in the number of recording elements.
It is another object of the invention to provide an improved method and apparatus for recording pixels that may be used to minimize artifacts resulting from nonuniformities such as in the positioning of the recording elements.